Derivative Instruments and Hedging Activities - Derivative Instruments Designated as Fair Value Hedges (Detail) (Interest rate swaps [Member], Interest expense [Member], USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Interest rate swaps [Member] | Interest expense [Member]
Derivatives And Hedging Activities [Line Items]
Gain / (Loss) on Instrument	$ 5.1	$ (3.3)
Gain / (Loss) on Hedged Item	$ (5.1)	$ 3.3